Apollo 12 was the sixth manned flight in the Apollo program and the second to land on the Moon. The mission was commanded by Charles "Pete" Conrad. It was launched on November 14, 1969, four months after Apollo 11. Conrad and Lunar Module Pilot Alan L. Bean performed just over one day and seven hours of lunar surface activity while Command Module Pilot Richard F Gordon remained in lunar orbit. The landing site for the mission was the Ocean of Storms. Key objectives were achievement of a more precise landing (which had not been achieved by Apollo 11), and to visit the Surveyor 3 probe to remove parts for analysis. The mission ended on November 24 with a successful splashdown having completed the main mission parameters successfully.

Launch and transfer

Apollo 12 launched on schedule, during a rainstorm. 36.5 seconds after lift-off from Kennedy Space Center, the vehicle triggered a lightning discharge through itself and down to the earth through the Saturn's ionized plume. Protective circuits on the fuel cells in the service module falsely detected overloads and took all three fuel cells offline, along with much of the CSM instrumentation. A second strike at 52 seconds after launch knocked out the "8-ball" attitude indicator. The telemetry stream at Mission Control was garbled nonsense. However, the Saturn V continued to fly correctly; the strikes had not affected the Saturn V's Instrument Unit.

The loss of all three fuel cells put the CSM entirely on batteries. They were unable to maintain normal 28V DC bus voltages into the heavy 75 amp launch loads. One of the AC inverters dropped offline. These power supply problems lit nearly every warning light on the control panel and caused much of the instrumentation to malfunction.

Legendary EECOMJohn Aaron (the original NASA "steely eyed missile man")[2] remembered the telemetry failure pattern from an earlier test when a power supply malfunctioned in the CSM Signal Conditioning Equipment (SCE). The SCE converts raw signals from instrumentation to standard voltages for the spacecraft instrument displays and telemetry encoders.[3]

Aaron made a call: "Try SCE to aux". This switched the SCE to a backup power supply. The switch was fairly obscure and neither the Flight Director, CAPCOM, nor Commander Conrad immediately recognized it. Lunar module pilot Alan Bean, flying in the right seat as the CSM systems engineer, remembered the SCE switch from a training incident a year earlier when the same failure had been simulated. Aaron's quick thinking and Bean's memory saved what could have been an aborted mission. Bean put the fuel cells back on line, and with telemetry restored, the launch continued successfully. Once in earth parking orbit, the crew carefully checked out their spacecraft before re-igniting the S-IVB third stage for trans-lunar injection. The lightning strikes had caused no serious permanent damage.

Initially it was feared that the lightning strike could have caused the command module's parachute mechanism to prematurely fire, disabling the explosive bolts that open the parachute compartment to deploy them. If they were indeed disabled, the command module would have crashed uncontrollably into the Pacific Ocean at the end of the mission and killed the crew instantly. Since there was no way to figure out whether or not this was the case, ground controllers decided not to tell the astronauts about the possibility. Fortunately, the parachutes did deploy and function nominally at the end of the mission.

After lunar module separation, the S-IVB was intended to fly into solar orbit. The S-IVB auxiliary propulsion system was fired and the remaining propellants vented to slow it down to fly past the moon's trailing edge (the Apollo spacecraft always approached the moon's leading edge). The moon's gravity would then slingshot the stage into solar orbit. However, a small error in the state vector in the Saturn's guidance system caused the S-IVB to fly past the moon at too high an altitude to achieve earth escape velocity. It remained in a semi-stable earth orbit after passing the Moon on November 18, 1969. It finally escaped earth orbit in 1971 but was briefly recaptured in Earth orbit 31 years later. It was discovered by amateur astronomer Bill Yeung who gave it the temporary designation J002E3 before it was determined to be an artificial object.

Landing

The Apollo 12 mission landed on an area of the Ocean of Storms that had been visited earlier by several unmanned missions (Luna 5, Surveyor 3, and Ranger 7). The International Astronomical Union, recognizing this, christened this region Mare Cognitum (Known Sea). The landing site would thereafter be listed as Statio Cognitum on lunar maps (Conrad and Bean did not formally name their landing site, interestingly enough, though the intended touchdown point was nicknamed Pete's Parking Lot by Conrad).

The second lunar landing was an exercise in precision targeting, using a Doppler Effect radar technique developed to allow the pinpoint landings needed for future Apollo missions.[4] Most of the descent was automatic, with manual control assumed by Conrad during the final few hundred feet of descent. Unlike Apollo 11 where Neil Armstrong took partial control of the lander and directed it further down range when he noticed that the intended landing site was strewn with boulders, Apollo 12 succeeded, on November 19, in landing within walking distance (less than 200 meters) of its intended target - the Surveyor 3 probe, which had landed on the Moon in April 1967. This was the first -- and, to date, only -- occasion in which humans have "caught up" to a probe sent to land on another world.

Conrad actually landed Intrepid 580 feet (180 m) short of Pete's Parking Lot because the planned landing point looked rougher than anticipated during the final approach to touchdown. The planned landing point was a little under 1,180 feet (360 m) from Surveyor 3, a distance that was chosen to eliminate the possibility of lunar dust (being kicked up by Intrepid's descent engine during landing) from covering Surveyor 3.[4] But the actual touchdown point — 600 feet (180 m) from Surveyor 3 — did cause a thin film of dust to coat the probe, giving it a light tan hue.

EVAs

When Conrad, who was somewhat shorter than Neil Armstrong, stepped onto the lunar surface, his first words were "Whoopie! Man, that may have been a small one for Neil, but that's a long one for me."[5] This was not an off-the-cuff remark: Conrad had made a $500 bet with reporter Oriana Fallaci he would say these words, after she had queried whether NASA had instructed Neil Armstrong what to say as he stepped onto the Moon. Conrad later said he was never able to collect the money.[6][7]

To improve the quality of television pictures from the Moon, a color camera was carried on Apollo 12 (unlike the monochrome camera that was used on Apollo 11). Unfortunately, when Bean carried the camera to the place near the lunar module where it was to be set up, he inadvertently pointed it directly into the Sun, destroying the vidicon tube. Television coverage of this mission was thus terminated almost immediately.[8]

Apollo 12 successfully landed within walking distance of the Surveyor 3 probe. Conrad and Bean removed pieces of the probe to be taken back to Earth for analysis. It is claimed that the common bacteriumStreptococcus mitis was found to have accidentally contaminated the spacecraft's camera prior to launch and survived dormant in this harsh environment for two and a half years.[9] However, this finding has since been disputed: see Reports of Streptococcus mitis on the moon.

Astronauts Conrad and Bean also collected rocks and set up equipment that took measurements of the Moon's seismicity, solar wind flux and magnetic field, and relayed the measurements to Earth. The instruments were part of the first complete nuclear-powered ALSEP station set up by astronauts on the moon to relay long-term data from the lunar surface. The previous Apollo 11 instruments were not as extensive or designed to operate long term. The astronauts also took photographs, although by accident Bean left several rolls of exposed film on the lunar surface. Meanwhile Gordon, on board the Yankee Clipper in lunar orbit, took multispectral photographs of the surface.

The lunar plaque attached to the descent stage of Intrepid is unique in that unlike the other lunar plaques, it (a) did not have a depiction of the Earth, and (b) it was textured differently (the other plaques had black lettering on polished stainless steel while the Apollo 12 plaque had the lettering in polished stainless steel while the background was brushed flat).

Return

Apollo 12 recovery by the USS Hornet.

Intrepid's ascent stage was dropped (per normal procedures) after Conrad and Bean rejoined Gordon in orbit. It impacted the Moon on November 20, 1969 at 3°56′S21°12′W﻿ / ﻿3.94°S 21.20°W﻿ / -3.94; -21.20. The seismometers the astronauts had left on the lunar surface registered the vibrations for more than an hour.

The crew stayed an extra day in lunar orbit taking photographs, for a total lunar surface stay of thirty-one and a half hours and a total time in lunar orbit of eighty-nine hours.

On the return flight to Earth after leaving lunar orbit, the crew of Apollo 12 witnessed (and photographed) a solar eclipse, though this one was of the Earth eclipsing the sun.

Yankee Clipper returned to Earth on November 24, 1969, at 20:58 UTC (3:58pm EST, 10:58am HST), approximately 500 miles (800 km) east of American Samoa. During landing, a 16 mm camera dislodged from storage and struck Bean in the forehead, rendering him briefly unconscious. He suffered a mild concussion, and needed six stitches.

Attempted stunts

Centerfold in lunar checklist

Alan Bean smuggled a camera-shutter self-timer device on to the mission with the intent of taking a photograph with himself, Pete Conrad and the Surveyor 3 probe in the frame. As the timer was not part of their standard equipment, such an image would have thrown post-mission photo analysts into confusion over how the photo was taken. However, the self-timer was misplaced during the EVA and the plan was never executed.

The Apollo 12 backup crew managed to insert into the astronaut's lunar checklist (attached to the wrists of Conrad's and Bean's spacesuits) reduced sized pictures of Playboy centerfolds, surprising Conrad and Bean when they looked through the checklist flip-book during their first EVA.[11] The Lunar Surface Journal website [1] contains a PDF with the photocopies of their cuff checklists showing these photos.[12] The checklists also contain two pages of pre-prepared complex geological terminology at the back, to be used for the confusion of the ground crew.

The artist Forrest (Frosty) Myers claims to have installed the art piece "Moon Museum" on "a leg of the Intrepid landing module with the help of an unnamed engineer at the Grumman Corporation after attempts to move the project forward through NASA's official channels were unsuccessful."[13]

Alan Bean left two mementos on the moon at Statio Cognitum: his silver astronaut pin, and Clifton Williams's pilot wings. Williams was originally scheduled as Apollo 12's lunar module pilot, but died in a training accident. The Apollo 12 mission patch contains four stars, one for each crew member and one in honor of Williams. Bean left his silver astronaut pin, signifying an astronaut who completed training but had not yet flown in space, for personal reasons. He was to get a gold astronaut pin for successfully completing the mission after the flight and felt he wouldn't need the silver pin thereafter.

Mission insignia

The Apollo 12 mission patch shows the crew's Navy background. It features a clipper ship arriving at the moon. The ship trails fire and flies the flag of the United States. The mission name APOLLO XII and the crew names are on a wide gold border, with a small blue trim. Blue and gold are traditionally Navy colors. The patch has four stars on it — one each for the three astronauts who flew the mission and one for Clifton Williams. Williams was killed on October 5, 1967, after a mechanical failure caused the controls of his T-38 trainer to stop responding. He trained with Conrad and Gordon as part of the back-up crew for what would be the Apollo 9 mission, and would have been assigned as Lunar Module pilot for Apollo 12.

Spacecraft location

Apollo 12 command module Yankee Clipper on display at the Virginia Air and Space Center in Hampton, Virginia.

The Apollo 12 Command Module Yankee Clipper is on display at Virginia Air and Space Center, Hampton, Virginia.

In 2002, astronomers thought they might have discovered another moon orbiting Earth, which they designated J002E3, that turned out to be the third stage of the Apollo 12 Saturn V rocket.[14]